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1.
高超声速边界层工程转捩模式研究 总被引：4，自引：0，他引：4
在流动从层流过渡到湍流的转捩区域,传统的湍流模式由于没有考虑到脉动的间歇性,因此不能很好给出转捩区域流动的发展过程。考虑湍流脉动的间歇性,引入间歇因子,根据Hassan构造湍流转捩模式的思想来建立基于SST湍流模式的湍流工程转捩模式。应用该工程转捩模式,数值模拟了轴对称高超音速尖锥绕流,计算结果与实验符合良好,表明作者发展的工程转捩模式可以成功应用于高超声速飞行器工程转捩问题的计算。 相似文献
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《中国科学院院刊(英文版)》2002,16(1)
1. Basic Research
Basic research has always been one of the major tasks of CAS. Over the more than 50 years since its founding, CAS has gradually branched out to cover many fundamental fields of the natural sciences, such as mathematics, physics, chemistry, mechanics,astronomy, space science, life science, geoscience and environmental science - with nearly 10,000 research professionals and 117 open laboratories (including 50 key State laboratories). At present, there are 29 research institutes (including observatories) covering such fields as physical science, mathematics, mechanics and astronomy; with 31 open laboratories (nine key State laboratories, four State laboratories and 18 CAS open laboratories). 相似文献
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Thanks to its unique features at the nanoscale, nanofluidics, the study and application of fluid flow in nanochannels/nanopores with at least one characteristic size smaller than 100 nm, has enabled the occurrence of many interesting transport phenomena and has shown great potential in both bio- and energy-related fields. The unprecedented growth of this research field is apparently attributed to the rapid development of micro/nanofabrication techniques. In this review, we summarize recent activities and achievements of nanofabrication for nanofluidic devices, especially those reported in the past four years. Three major nanofabrication strategies, including nanolithography, microelectromechanical system based techniques, and methods using various nanomaterials, are introduced with specific fabrication approaches. Other unconventional fabrication attempts which utilize special polymer properties, various microfabrication failure mechanisms, and macro/microscale machining techniques are also presented. Based on these fabrication techniques, an inclusive guideline for materials and processes selection in the preparation of nanofluidic devices is provided. Finally, technical challenges along with possible opportunities in the present nanofabrication for nanofluidic study are discussed. 相似文献
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机电液一体化技术及其在工业机器人中的应用 总被引：1，自引：0，他引：1
概述了“机电液一体化”在工程机械中的意义及其所包含的内容.概括了国内外机电液一体化技术在工业机器人中的发展概况.从液压系统的高压化、电子器件的灵敏化与智能化、节能增效、软件平台的重要作用、智能机群的协同作业、ER流体技术等6个方面阐述了机电液一体化技术在工业机器人中的发展趋势.指出了加强机、电、液一体化的程度将是我国发展工业机器人的关键. 相似文献
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模拟跨声速湍流的线性和非线性涡粘性湍流模式 总被引：1，自引：0，他引：1
讨论应用线性和非线性涡粘性湍流模式计算跨声速湍流 .用于比较的 3个线性湍流模式是Shih和Lumley的k ε模式 ,CMOTT模式和SST模式 .2个非线性模式是Shih ,Zhu和Lumleyd的二阶模式 ,以及Shih等的三阶模式 .计算的典型流动是绕凸起的跨声速流动 ,该流动的特征是激波与边界层相互作用且伴有流动分离 .计算结果表明非线性湍流模式具有明显的优势 . 相似文献
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Focusing and sorting cells and particles utilizing microfluidic phenomena have been flourishing areas of development in recent years. These processes are largely beneficial in biomedical applications and fundamental studies of cell biology as they provide cost-effective and point-of-care miniaturized diagnostic devices and rare cell enrichment techniques. Due to inherent problems of isolation methods based on the biomarkers and antigens, separation approaches exploiting physical characteristics of cells of interest, such as size, deformability, and electric and magnetic properties, have gained currency in many medical assays. Here, we present an overview of the cell/particle sorting techniques by harnessing intrinsic hydrodynamic effects in microchannels. Our emphasis is on the underlying fluid dynamical mechanisms causing cross stream migration of objects in shear and vortical flows. We also highlight the advantages and drawbacks of each method in terms of throughput, separation efficiency, and cell viability. Finally, we discuss the future research areas for extending the scope of hydrodynamic mechanisms and exploring new physical directions for microfluidic applications. 相似文献
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国外知识集成研究综述 总被引：4，自引：1，他引：4
本文对知识管理中的研究重点和热点———知识集成的概念、现状和发展趋势进行了综述。由于对知识集成本身的研究时间不长,因此无论是在理论和实践中都缺乏系统性的研究,形成了研究的丛林。本文通过详实的文献,阐述了知识集成的概念,分析了知识集成模型和机理,讨论了知识集成的途径、隐性知识获取等多个关键问题和主要进展。在此基础上,对今后主要的研究方向和重点问题进行了探讨。 相似文献
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随着数字图书馆中数字视频资源的增长,数字视频版权保护问题逐渐暴露出来。基于内容的视频拷贝检测技术作为一种有效的版权保护技术,近年来逐渐受到研究人员的关注。本文对基于内容的视频拷贝检测的关键技术视频指纹提取和指纹匹配的研究成果进行了分析,总结了指纹提取和指纹匹配的研究现状,指出了该领域存在的问题,最后分析了该领域的发展方向。 相似文献
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Microfluidic techniques have been recently developed for cell-based assays. In microfluidic systems, the objective is for these microenvironments to mimic in vivo surroundings. With advantageous characteristics such as optical transparency and the capability for automating protocols, different types of cells can be cultured, screened, and monitored in real time to systematically investigate their morphology and functions under well-controlled microenvironments in response to various stimuli. Recently, the study of stem cells using microfluidic platforms has attracted considerable interest. Even though stem cells have been studied extensively using bench-top systems, an understanding of their behavior in in vivo-like microenvironments which stimulate cell proliferation and differentiation is still lacking. In this paper, recent cell studies using microfluidic systems are first introduced. The various miniature systems for cell culture, sorting and isolation, and stimulation are then systematically reviewed. The main focus of this review is on papers published in recent years studying stem cells by using microfluidic technology. This review aims to provide experts in microfluidics an overview of various microfluidic systems for stem cell research. 相似文献
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高校工科实验基地过渡到创新基地途径的探讨 总被引：3，自引：0，他引：3
考察了工科实验基地过渡到创新基地的途径。通过主动发展高技术衍生创新基地、依靠学科特色培育创新基地、通过学科交叉催化创新基地、利用高级别科学研究推动实验基地过渡几个方面讨论了具体的实现方式;分析了工科实验基地过渡的作用机理和若干要点;提出了保障、促进工科实验基地过渡的若干建议。 相似文献
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情境感知技术是泛在环境的关键技术之一,逐渐成为近些年的研究热点。文章介绍情境、情境感知和情境感知技术的概念,探讨情境感知技术在图书馆中的具体应用,提出情境感知图书馆框架结构,分析图书馆应用情境感知技术可能的提供的一些服务。 相似文献
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Blockchain technology provides us a new tool to solve the product traceability problem in supply chain management. This research focuses on the cross-border e-commerce context, to propose a blockchain-based framework, and develop a set of corresponding techniques and methods for achieving traceable products and transactions in supply chain management. A general blockchain-based product traceability framework is introduced. This framework is based on a cross-border e-commerce supply chain context, incorporating a series of blockchain-based models, including multi-chain structure model, data management model and block structure model. Several core methods and algorithms are also developed, such as information anchoring method, key distribution method, information encryption algorithm and anti-counterfeiting method. The framework, models and methods form a complete and comprehensive solution, which are evaluated by applying to several typical problems and attack cases. The case analysis results show that the framework, models and methods can successfully deal with key recover problem, and protect against clone attack, counterfeit tag attack and counterfeit product attack. The effectiveness, extendibility, security, implementation and governance issues of applying these solutions are also discussed. This research contributes to the theoretical and practical literatures on blockchain technology, cross-border e-commerce and supply chain management research fields. 相似文献
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以农业部-CABI生物安全联合实验室为例,阐述一个国际合作与交流成效显著的国际联合实验室运转需具备的要素,明确的目标和定位、持续的研究发展方向、良好的管理体制、完善的运行机制、优秀的科研人才及创新团队、多渠道的全球科技资源与社会资源。通过国际联合实验室的建设与共享,寻求国外优势力量,广泛开展国际交流与合作,在引进聚集高端人才及组建国际化科研创新团队、谋划申请国际合作项目、引进优质资源和关键技术、承担国际会议促进我国科学家与国际同行交流、加强南南合作促进我国农业科技"走出去"、推广农业科技促进农业可持续发展等方面起到了积极的推动作用。 相似文献
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Living cells are a fascinating demonstration of nature’s most intricate and well-coordinated micromechanical objects. They crawl, spread, contract, and relax—thus performing a multitude of complex mechanical functions. Alternatively, they also respond to physical and chemical cues that lead to remodeling of the cytoskeleton. To understand this intricate coupling between mechanical properties, mechanical function and force-induced biochemical signaling requires tools that are capable of both controlling and manipulating the cell microenvironment and measuring the resulting mechanical response. In this review, the power of microfluidics as a functional tool for research in cell mechanics is highlighted. In particular, current literature is discussed to show that microfluidics powered by soft lithographic techniques offers the following capabilities that are of significance for understanding the mechanical behavior of cells: (i) Microfluidics enables the creation of in vitro models of physiological environments in which cell mechanics can be probed. (ii) Microfluidics is an excellent means to deliver physical cues that affect cell mechanics, such as cell shape, fluid flow, substrate topography, and stiffness. (iii) Microfluidics can also expose cells to chemical cues, such as growth factors and drugs, which alter their mechanical behavior. Moreover, these chemical cues can be delivered either at the whole cell or subcellular level. (iv) Microfluidic devices offer the possibility of measuring the intrinsic mechanical properties of cells in a high throughput fashion. (v) Finally, microfluidic methods provide exquisite control over drop size, generation, and manipulation. As a result, droplets are being increasingly used to control the physicochemical environment of cells and as biomimetic analogs of living cells. These powerful attributes of microfluidics should further stimulate novel means of investigating the link between physicochemical cues and the biomechanical response of cells. Insights from such studies will have implications in areas such as drug delivery, medicine, tissue engineering, and biomedical diagnostics. 相似文献
17.
短期太阳能光伏发电预测方法研究进展 总被引：3，自引：0，他引：3
提高短期光伏发电预测水平是太阳能光伏发电站并入现有电网系统和太阳能光伏开发利用的关键问题,对提高太阳能光伏发电开发利用、保证并网安全也具有重要意义.本文对国内外短期太阳能光伏发电预测方法进行了分类归纳总结,对各类方法的发展趋势、优缺点等进行了分析.结果表明,统计智能类预测方法是国内外小型光伏电站短期光伏发电量预测技术发展的重点,总体平均预测误差在3.0％～ 11.0％之间.简单物理模型类预测方法是目前国内外大中型并网光伏电站业务运行采用最多的短期光伏发电量预测方法,总体平均预测误差在5.0％～20.0％之间.复杂物理模型类预测方法是未来大型光伏电站短期发电量预测技术研究和发展应用的主要方向.文章结论对我国短期太阳能光伏发电预测技术的发展具有促进作用. 相似文献
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《Journal of The Franklin Institute》2021,358(16):8169-8192
An adaptive dynamic programming controller based on backstepping method is designed for the optimal tracking control of hypersonic flight vehicles. The control input is divided into two parts namely stable control and optimal control. First, the back-stepping method is exploited via neural networks (NNs) to estimate unknown functions. Then, the computational load is reduced by the minimal-learning-parameter (MLP) scheme. To avoid the problem of “explosion of terms”, a first-order filter is adopted. Next, the optimal controller is designed based on the adaptive dynamic programming. In order to solve the Hamiltonian equation, NNs estimators are introduced to approximate performance indicators, achieving the approximate optimal control of hypersonic flight vehicles. Finally, the effectiveness and advantages of the control method are verified by simulation results. 相似文献
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What's Wrong with the 'Golden Rule'? Conundrums of Conducting Ethical Research in Cyberspace 总被引：2，自引：0，他引：2
Christina Allen 《The Information Society》1996,12(2):175-188
Three key values for ethical cyberspace research practices are evident in recent discussions: (1) protect the subjects from harm as a result of the research fieldwork and the research practices; (2) produce good social science research; and (3) do not unnecessarily perturb the phenomena studied. Much of the argumentation aims to negotiate the ethical conflicts that often emerge between these goals. Bakhtin argues that one can only strive for a bottom-up ethical wisdom built upon concrete examples, and disputes the possibility that rigid top-down application of universal rules constitutes ethical action. His perspective has key implications for ethical research practices. I illustrate this perspective at work through my recent fieldwork and writing practices in a virtual community. Research ethics for cyberspace are like research ethics for any other site. They should be situated, dialogic agreements that develop over time between researchers and the participants of the research study. It is unlikely that such research ethics can be abstractly codified, because there will often be differences between research sites, the situations of participants, and researcher goals. Researchers can, however, develop ethical wisdom that comes from experience with many configurations of research in cyberspace, and report on the conditions that grounded their ethical choices, and the results that emerged from their work in the site. These results will often be improved by feedback from participants about their experiences with the fieldwork and the effects of publication. 相似文献
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流体力学是关于流体机械运动规律及其应用的一门学科,它主要是研究流体之间的相互力的作用,包括流体与流体、壁面与流体、流体与其他等方面。流体力学是一门与人类生活息息相关的学科,并且众多理工学科的基本专业知识都是流体力学,它所包含的理论知识和实验对于专业课学习、学生毕业设计、实际工程问题等起着重要的理论支撑和指导作用。所以流体力学的教学在工科高等院校显得尤为重要。 相似文献